In IE 5.2 (and previous versions) under Interface Extras, you can specify that IE should open a new browser window when a URL is requested by another application. I noticed an anomaly in the way this preference works.
It works great when other apps tell IE to load a URL. However, when you double-click a file that has the extension .URL, it will open the URL in the frontmost browser window ... it does NOT open a new window.
Interestingly enough, if the same URL file is named with the extension .webloc, then IE does the right thing and opens the URL in a new window.
Bug or feature?
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020628083744233